You're going to have problems with this. To start, your SQL server is a DC, which means it has no local accounts. Unless you changed the other web servers, they are running under local accounts for anonymous user and the ASP.NET process. Which means a restore to the DC won't have the correct security. The second problem will be your running IISBACK on each server and restoring three to one. Last one wins. No gurantees on what will work, if anything.
You'd be far better off combining all sites onto one server and replic ate to the other two servers. Use NLB to handle fail over. You could script Robocopy to copy content, web sites may be a bit harder but you configure once and you're done.
Jeff
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